Shanghai’s long, stale summer may be just heating up, but the Chinese art markethas been boiling over for months already. Zhang Xiaogang’s "Bloodline" paintings are especially popular -- in March Sotheby’s New York sold one of the dour grey portraits for $2.11 million, a record price for a work from the series. Material from China’s tumultuous history is also hotly pursued, as indicated by the record sale of Xu Beihong’s subtly political World War II-era painting Put Down Your Whip (1939) for $9.2 million in Hong Kong.